In many areas of the world, large buildings and other structures may periodically be subjected to seismic or other loads (e.g., earthquakes, wind, weather related events, explosive blasts). In order to prevent structures from being damaged by such loads, particularly the displacements that follow the application of seismic loads to structures, or to at least reduce the amount of damage that loading may cause to such structures, various devices have been developed to absorb such displacements to reduce the loading experienced by other elements of the structure.
One such device is commonly referred to as a “buckling restrained brace.” A buckling restrained brace may include an elongate yielding core element connected at two ends to a building frame, e.g., diagonally across a rectangular “bay” formed by two horizontal frame members and two vertical frame members. Plastic deformation of the yielding core element under applied forces can absorb a significant amount of energy and may mitigate or prevent damage to other elements of the building structure. The yielding core element is typically surrounded by a sleeve configured to allow the core element to lengthen in response to applied tensile forces, while hindering or preventing the yielding core element from buckling under compressive forces by providing the yielding core with lateral support.
In many buckling restrained braces, the sleeve includes a metal shell within which an annular layer of grout or cement is formed. The grout or cement material may be separated from the yielding core by a layer of, e.g., polymer material or by a small gap (i.e., void). For example, a buckling restrained brace featuring such an arrangement is described in U.S. Pat. No. 7,188,452 to Sridhara, filed Mar. 11, 2003, and issued Mar. 13, 2007, the disclosure of which is incorporated herein in its entirety by this reference.